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cgroups/cgfsng: do not prematurely close file descriptors
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When adding the new improved cgroup setup logic I didn't account for the fact
that we need the hierarchy fds up until chown. Add a dedicated cleanup method
to fix this:

lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, , 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, tasks, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, cgroup.procs, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, , 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, tasks, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, cgroup.procs, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, , 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, tasks, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, cgroup.procs, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, , 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, tasks, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, cgroup.procs, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, , 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, tasks, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, cgroup.procs, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, , 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, tasks, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, cgroup.procs, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, , 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, tasks, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, cgroup.procs, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, , 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, tasks, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, cgroup.procs, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, , 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, tasks, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, cgroup.procs, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, , 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, tasks, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, cgroup.procs, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, , 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, tasks, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, cgroup.procs, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, , 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, tasks, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )
lxc b1 20191212205052.712 WARN     cgfsng - cgroups/cgfsng.c:fchowmodat:1481 - Bad file descriptor - Failed to fchownat(-9, cgroup.procs, 1000000000, 0, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )

Closes #3228.
Fixes: 1973b62 ("cgroups/cgfsng: improve cgroup creation and removal")
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
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Christian Brauner committed Dec 13, 2019
1 parent c8f4313 commit 5d56242
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Showing 3 changed files with 28 additions and 11 deletions.
35 changes: 24 additions & 11 deletions src/lxc/cgroups/cgfsng.c
View file
Expand Up @@ -1413,9 +1413,9 @@ __cgfsng_ops static bool cgfsng_monitor_enter(struct cgroup_ops *ops,
return log_error_errno(false, errno, "Failed to enter cgroup \"%s\"", h->monitor_full_path);

/*
* We don't keep the fds for non-unified hierarchies around
* we don't keep the fds for non-unified hierarchies around
* mainly because we don't make use of them anymore after the
* core cgroup setup is done but also because they're quite a
* core cgroup setup is done but also because there are quite a
* lot of them.
*/
if (!is_unified_hierarchy(h))
Expand Down Expand Up @@ -1453,15 +1453,6 @@ __cgfsng_ops static bool cgfsng_payload_enter(struct cgroup_ops *ops,
ret = lxc_writeat(h->cgfd_con, "cgroup.procs", pidstr, len);
if (ret != 0)
return log_error_errno(false, errno, "Failed to enter cgroup \"%s\"", h->container_full_path);

/*
* We don't keep the fds for non-unified hierarchies around
* mainly because we don't make use of them anymore after the
* core cgroup setup is done but also because they're quite a
* lot of them.
*/
if (!is_unified_hierarchy(h))
close_prot_errno_disarm(h->cgfd_con);
}

return true;
Expand Down Expand Up @@ -1582,6 +1573,27 @@ __cgfsng_ops static bool cgfsng_chown(struct cgroup_ops *ops,
return true;
}

__cgfsng_ops void cgfsng_payload_finalize(struct cgroup_ops *ops)
{
if (!ops)
return;

if (!ops->hierarchies)
return;

for (int i = 0; ops->hierarchies[i]; i++) {
struct hierarchy *h = ops->hierarchies[i];
/*
* we don't keep the fds for non-unified hierarchies around
* mainly because we don't make use of them anymore after the
* core cgroup setup is done but also because there are quite a
* lot of them.
*/
if (!is_unified_hierarchy(h))
close_prot_errno_disarm(h->cgfd_con);
}
}

/* cgroup-full:* is done, no need to create subdirs */
static bool cg_mount_needs_subdirs(int type)
{
Expand Down Expand Up @@ -3253,6 +3265,7 @@ struct cgroup_ops *cgfsng_ops_init(struct lxc_conf *conf)
cgfsng_ops->payload_delegate_controllers = cgfsng_payload_delegate_controllers;
cgfsng_ops->payload_create = cgfsng_payload_create;
cgfsng_ops->payload_enter = cgfsng_payload_enter;
cgfsng_ops->payload_finalize = cgfsng_payload_finalize;
cgfsng_ops->escape = cgfsng_escape;
cgfsng_ops->num_hierarchies = cgfsng_num_hierarchies;
cgfsng_ops->get_hierarchies = cgfsng_get_hierarchies;
Expand Down
1 change: 1 addition & 0 deletions src/lxc/cgroups/cgroup.h
View file
Expand Up @@ -166,6 +166,7 @@ struct cgroup_ops {
struct lxc_handler *handler);
bool (*monitor_delegate_controllers)(struct cgroup_ops *ops);
bool (*payload_delegate_controllers)(struct cgroup_ops *ops);
void (*payload_finalize)(struct cgroup_ops *ops);
};

extern struct cgroup_ops *cgroup_init(struct lxc_conf *conf);
Expand Down
3 changes: 3 additions & 0 deletions src/lxc/start.c
View file
Expand Up @@ -1916,6 +1916,9 @@ static int lxc_spawn(struct lxc_handler *handler)
}
}

cgroup_ops->payload_finalize(cgroup_ops);
TRACE("Finished setting up cgroups");

/* Run any host-side start hooks */
ret = run_lxc_hooks(name, "start-host", conf, NULL);
if (ret < 0) {
Expand Down

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